The present disclosure relates to a controller for controlling an internal combustion engine that includes a valve timing adjuster, which adjusts the rotational phase of the camshaft relative to that of the engine output shaft, and a variable valve lift mechanism, which changes the maximum valve lift and the opening duration of engine valves.
Japanese Laid-Open Patent Publication No. 2011-149325 discloses one example of such a controller for controlling an internal combustion engine that includes a valve timing adjuster, which adjusts the rotational phase of the camshaft relative to that of the engine output shaft, and a variable valve lift mechanism, which changes the maximum valve lift and the opening duration of engine valves.
For example, the variable valve lift mechanism disclosed in Japanese Laid-Open Patent Publication No. 2012-246780 includes a control shaft that moves in the axial direction based on driving of a motor. A target is attached to the control shaft, and the amount of movement of the target in the axial direction is detected by a sensor. Accordingly, the movement amount of the control shaft, which is the driven amount of the variable valve lift mechanism, is obtained. Through control of the movement amount of the control shaft, the maximum valve lift and the opening duration of engine valves are adjusted.
Some internal combustion engines with variable valve lift mechanisms perform abnormality diagnosis for the variable valve lift mechanisms. Methods for such abnormality diagnosis include a method that compares an estimated value of the movement amount of the control shaft, which is calculated from the driven amount of the motor, with the movement amount of the target, which is detected by a sensor as described above. In this case, however, the sensor and the target must be installed in the variable valve lift mechanism, which increases the costs for the entire engine.